Human Immunodeficiency Virus (“HIV”), the virus that causes AIDS, has reached pandemic proportions in the world. Some one million people are infected with HIV in the U.S. alone, and more than forty million worldwide. Each day, approximately 12,000 adults and 1,800 children become infected. Currently, there are three classes of drug treatments for HIV, namely, reverse transcriptase (“RT”) inhibitors, such as AZT (3′-azido-3′-deoxythymidine), protease inhibitors, and fusion inhibitors. Common HIV drug therapy includes a cocktail drug regiment, which may utilize, for example, nucleoside analogs like AZT, 2′,3′-dideoxyinosine, and 2′,3′-dideoxycytidine. These drugs act through the inhibition of the HIV reverse transcriptase activity and/or by a mechanism of oligonucleotide chain termination.
However, these currently acceptable treatment drugs are limited by either their toxicity or the emergence of drug-resistant HIV strains (Evers et al., J. Med. Chem. 39:1056-1063 (1996)). In addition, these drugs are costly, difficult to manufacture, and have adverse side effects. Subjects also frequently develop resistance to these drugs. Therefore, the search for new types of anti-HIV compounds is timely and important.
Betulin, or betulinol, is one of the more plentiful triterpenes, constituting up to twenty-four percent of the outer bark of the white birch (Betula alba) and as much as thirty-five percent of the outer bark and about five percent of the inner bark of the Manchurian white birch (Betula platyphylla) (Hirota et al., J.S.C.I. Japan 47:922 (1944)). Betulin also occurs in a free state in the bark of yellow and black birch (Steiner, Mikrochemie, Molisch-Festschrift, p. 405 (1936)), Corylus avellana and Carpinus betulus (Feinberg et al., Monatsh 44:261 (1924); Brunner et al., Monatsh 63:368 (1934); Brunner et al., Monatsh 64:21 (1934)), and Lophopetalum toxicum (Dieterle et al., Arch. Pharm. 271:264 (1933)). The exudate from the bark of Trochodendron aralioides, which constitutes Japanese bird-lime, contains betulin palmitate (Shishido et al., J.S.C.I. Japan 45:436 (1942)). Betulin has also been isolated from rosehips (Zimmermann, Helv. Chim. Acta 27:332 (1944)) and from the seeds of Zizyphus vulgaris Lamarck var. spinosus Bunge (Rhamnaceae) (Kawaguti et al., J. Pharm. Soc. Japan 60:343 (1940)). Ruhemann et al., Brennstoff-Ch. 13.341 (1932) discloses the presence of betulin, allobetulin, and an “oxyallobetulin” in the saponifiable portion of a benzene-alcohol extract of mid-German brown coal. In addition, the following group of lupon-row derivatives from the birch cortex extract have been identified: (a) betulinol, (b) betulinic acid, (c) betulin aldehyde, (d) betulonic acid, and (e) betulone aldehyde (Rimpler et al., Arch. Pharm. Und. Ber. Dtsh. Ppharmaz Jes. 299:422-428 (1995); Lindgren et al., Acta Chem. 20:720 (1966); and Jaaskelainen, P. Papperi Ja Puu-Papper Och Tra. 63:599-603 (1989)).
Birch tree cortex-extracted betulinol was first mentioned as an antiseptic in 1899. Subsequently, compounds singled out from extracts of Hyptis emory and Alnus oregonu, identified as pentacyclic styrenes and their derivatives, were shown to inhibit carcinosarcoma growth (Sheth et al., J. Pharm. Sci. 61:1819 (1972); Sheth et al., J. Pharm. Sci. 62:139-140 (1973)). It has been suggested that betulinic acid is the main anti-tumor agent in the mixture of terpenoids (Tomas et al., Planta Medicina 54:266-267 (1988); Ahmat et al., J. Indian Chem. Soc. 61:92-93 (1964)). In particular, betulinic acid showed cytotoxic activity against carcinoma cell line CO-115 of the large intestine (LD 50-0.375 mg/ml) (Ukkonen et al., Birch Bark Extractive Kenzia Keini 6:217 (1979)). U.S. Pat. No. 6,890,533 to Bomshteyn et al., discloses betulinol derivatives and betulinol-antibody conjugates useful in treating cancer.
Betulinol (lup-20(29)-ene-3.beta., 28-diol) is commercially available (e.g., Sigma Chemical Co., St. Louis, Mo.) and is described for example, in “Merck 1212,” The Merck Index, 11th ed. (1989), and Simonsen et al., The Terpenes Vol. IV, Cambridge U. Press, pp. 187-328 (1957).
The chemical structure of betulinol is:

Betulinol has been shown to have anti-viral activity, including anti-herpes virus activity (U.S. Pat. No. 5,750,578 to Carlson et al.) and anti-HIV activity (U.S. Pat. No. 6,172,110 to Lee et al.; Sun et al., J. Med. Chem. 41:4648-4657 (1998)). Certain betulinol derivatives have also been investigated with regard to potential for anti-viral activity.
Betulonic acid and derivatives thereof (Hashimoto et al., Bioorg. Med. Chem. 5:2133-2143 (1997); Sun et al., J. Med. Chem. 41:4648-4657 (1998)), betulinic acid and derivatives thereof, dihydrobetulinic acid and derivatives thereof (Hashimoto et al., Bioorg. Med. Chem. 5:2133-2143 (1997); Sun et al., J. Med. Chem. 45:4271-4275 (2002); Kashiwada et al., Bioorg. Med. Chem. Lett. 11:183-185 (2001); Kashiwada et al., J. Med. Chem. 39:1016-1017 (1996); Flekhter et al., Bioorg. Khim. 28:543-550 (2003); “Betulinic Acid Derivatives in AIDS,” Marketletter (May 2, 1994); DeClercq, Med. Res. Rev. 20:323-349 (2000); Vlietinck et al., Plant Med. 64:97-109 (1998); Soler et al., J. Med. Chem. 39:1069-1083 (1996); Evers et al., J. Med. Chem. 39:1056-1068 (1996); U.S. Pat. Nos. 5,468,888 to Bouboutou et al., 5697828 to Lee et al., 5,869,535, 6,225,353, 6495600, and 6569842 to Pezzuto, 6048847 to Ramadoss et al., and 6403816 to Jaggi et al.; and PCT Application Publication No. WO 96/39033 to Lee et al.), betulin diacetate (Sun et al., Med. Chem. 41:4648-4657 (1998)), and betulone aldehyde (U.S. Pat. Nos. 5,869,535, 6,225,353 and 6,495,600 to Pezzuto et al.) have been investigated with regard to potential for anti-HIV activity. In addition, certain betulin derivatives, including betulin diacetate (U.S. Pat. No. 5,750,578 to Carlson) and betulinic acid (U.S. Pat. No. 6,214,350 to Hwang) have been shown to exhibit anti-herpes virus activity.
Unfortunately, however, many of these betulinol derivative compounds have significant drawbacks to their use. Betulin diacetate and betulonic acid, for example, have been shown to exhibit a low therapeutic index (Sun et al., J. Med. Chem. 41:4648-4657 (1998)). In addition, certain betulinic acid derivatives, such as betulonic acid, have been found to be cytotoxic, interfering with the proliferation of cells (Hashimoto et al., Bioorg. Med. Chem. 5:2133-2143 (1997)). In addition, no current anti-HIV agent, with the exception of α-interferon, has any effect on release of virus from a chronically infected cell. Thus, the search for new anti-HIV compounds remains timely and important.
Betulinol derivatives in general, and betulonic acid in particular, are soluble in a number or organic solvents such as ethanol and DMSO. However, betulonic acid and the known betulinol derivatives are generally insoluble in aqueous environment or other pharmaceutically acceptable solvents. Good solubility in an aqueous environment is an important property for a pharmaceutical agent. Absent this property, administration of the pharmaceutical agent to mammals can be difficult and biological activity in such mammals (including humans) may be impeded or entirely absent. Due to their limited solubility in aqueous solutions, the use of terpenoids such as betulinol and it derivatives as pharmaceuticals has been limited. To be effective as a pharmaceutical agent, especially for oral ingestion, water soluble betulinol derivatives would be desirable.
The present invention is directed to overcoming these and other deficiencies in the art.